A PETITION FOR THE INTRODUCTION AND FIELD RELEASE OF THE CHONDRILLA ROOT MOTH, BRADYRRHOA GILVEOLELLA (TREITSCHKE), FOR THE BIOLOGICAL CONTROL OF RUSH SKELETONWEED IN NORTH AMERICA Submitted by J. L. Littlefield1, J. Birdsall2, J. Helsley3, and G. Markin4 1 Research Entomologist. Department of Entomology, Montana State University, PO Box 173020, Bozeman, MT 59717- 3020. Phone: (406) 994-4722, Fax: (406) 994-5587, e-mail: [email protected] 2 Botanist. U.S. Forest Service, Rocky Mountain Research Station, Forestry Sciences Laboratory, Montana State University, Bozeman, MT 59717-2780. Phone: (406) 994-1784, Fax: (406) 994-5916, e-mail: jbirdsall/[email protected] 3 Research Assistant. Department of Entomology, Montana State University, PO Box 173020, Bozeman, MT 59717-3020. 4 Research Entomologist. U.S. Forest Service, Rocky Mountain Research Station, Forestry Sciences Laboratory, Montana State University, Bozeman, MT 59717-2780. Phone: (406) 994-4892, Fax: (406) 994-5916. TABLE OF CONTENTS Page ABSTRACT 1 I. INTRODUCTION 1 Nature of the Problem 1 1. History of Introduction and Spread 1 2. Present Distribution in North America 1 3. Sectors Affected and Magnitude of the Problem 1 4. Consensus that the Weed is a Suitable Target for Control 2 Proposed Action 2 II. TARGET WEED INFORMATION 2 Taxonomy of the Target Weed 2 1. Classification 2 2. Identifier 2 3. Problems in identification or taxonomy 3 4. Origin and location of herbarium specimens and the date of depository 3 Description of the Target Weed 3 Distribution of the Target Weed 3 1. Native Range 3 2. Worldwide Areas of Introduction, Pattern of Movement, and Limit 5 3. Present distribution in North America 5 4. Area of Potential Spread in North America 5 5. Information on Genetic Variability 6 6. Habitats/Ecosystems Where Weed is Found in North America 7 Taxonomically Related Plants and Their Distribution 7 Life History of the Target Weed 7 Impacts of the Target Weed 8 1. Beneficial Uses 8 2. Social and Recreation Use 8 3. Impact on Threatened and Endangered Species 8 4. Economic Losses 8 5. Health Dangers 8 6. Regulatory Aspects 9 7. Effects on native plant and animal populations. 9 8. Impact of current weed control on non-target plants 9 i Contents (cont.) Page 9. Effect on ecosystem functions and ecological relationships 9 Alternative Management Options 9 1. Historical Options 9 2. Current Options. 10 3. Potential Options 10 III. BIOLOGICAL CONTROL AGENT INFORMATION 11 Taxonomy of Bradyrrhoa 11 1. Common Names 11 2. Classification 11 3. Synonymy 11 4. List of closely related taxa in North America 11 5. Identification of Bradyrrhoa 11 Who identified agent, names and locations 11 Description of life stages 11 Problems in identification 12 Voucher specimens 12 Who identified the Agent 12 Reason for choosing agent 12 Geographical Range 12 1. Native Range 12 2. Other Areas of Introduction 12 3. Expected range in North America 12 4. Geographical range of closely related taxa in North America 12 Life History 13 1. Biology 13 2. Known Mortality Factors 13 3. Known Host Range (Specificity) 14 Field Observations 14 Laboratory Observations (Host Specificity Testing) 14 Populations of the Agent Studied 14 Sites of Study 14 Experimental Methodology, Analysis and Host Range Testing 14 Previous Host Specificity Testing (Caresche and Wapshere 1975) 14 Purpose 14 Test Plant List 14 Agent Source 14 Target Source 14 # Replicates 14 ii Contents (cont.) Page Methods 15 Results 15 Host Specificity Testing (Littlefield, Birdsall, Markin, and Helsley 1997-1999) 18 Purpose 18 Test Plant List 18 Agent Source 18 Target Source 19 # Replicates 19 Methods 19 Rearing 19 Oviposition 19 Host Testing 20 Results 20 Results 1997 20 Results 1998 20 Results 1999 21 Discussion 22 Host specialization 22 Potential impact on native species 22 Potential impact on threatened, endangered and sensitive species 24 Potential impact on plant populations 25 Habitat and climatic suitability 26 IV. PROTOCOL FOR RELEASING THE AGENT 26 Geographical or Host Source 26 Method to Ensure Proper Identification 26 Protocol to Ensure the Absence of Natural Enemies 26 Impact of Other Management Practices 26 Specific Location of Rearing Facility 26 Intended Sites for Initial Release 26 Number of Moths to be Released 27 Timing of Releases 27 Release Methods 27 iii Contents (cont.) Page V. POTENTIAL ENVIRONMENTAL IMPACTS 27 Human Impacts 27 1. Recreational 27 2. Aesthetics 27 3. Health Risks 27 Potential Economic Impacts 27 Plant Impacts 28 Nonplant Impacts 28 Preventive/ Mitigating Methods 28 Abiotic/Edaphic Effects 28 Petitioner’s Perspective of Risk 28 Outcome of No Action 29 Conclusion 29 VI. ACKNOWLEDMENTS 29 VII. REFERENCES 30 APPENDIX I. 35 iv ABSTRACT: Rush skeletonweed, Chondrilla juncea L. (Asteraceae), is considered a noxious weed in many western states and is currently a target for biological control. Bradyrrhoa gilveolella (Treitschke) (Lepidoptera: Pyralidae) is a root-feeding moth being considered for use in the biological control of rush skeletonweed. This organism will serve to complement the existing biocontrol agents that have been established on rush skeletonweed in the Pacific Northwest but have provided only limited suppression of the weed. Although root feeders have suppressed populations of several noxious weeds in the western US, no root feeding organisms have been introduced into North America for this particular weed species. Host records (field) and laboratory studies indicate that the moth is restricted to the genus Chondrilla; and only C. juncea occurs in North America. Since the moth is genus specific there would be negligible risk to other related plant genera, including the closely related genera of Taraxacum and Crepis. We thereby recommend the release of this moth into North America. I. INTRODUCTION Nature of the Problem 1. History of Introduction and Spread. Chondrilla juncea L. (rush skeletonweed) arrived in the eastern United States in the early nineteenth century as a weed seed in European grain (Reed 1979). In the western United States, rush skeletonweed was first reported near Spokane, Washington in 1938. Rush skeletonweed was reported in Idaho and Oregon in the 1960s and by 1995 infested over 6.2 million acres of rangeland in the Pacific Northwest and California (Sheley and Hudak 1995). It is estimated that the infestation of rush skeletonweed in the Pacific Northwest increases 41,000 ha per year (Spollen and Piper 1995). This weed was first reported in Montana in 1991 (Sheley and Hudak 1995). Rush skeletonweed is currently increasing in the Pacific Northwest, as evidenced by the rise in number of infested counties from close to zero in 1938 to over 50 in 1999 (New Invaders Database 1999). Viewing a plot of these figures, rush skeletonweed appears to be on an exponential increase in the Northwest and may indicate the potential for rapid spread in western North America. 2. Present Distribution in North America. The present distribution of rush skeletonweed in the United States includes the following states: California, Delaware, Georgia, Idaho, Indiana, Maryland, Michigan, Montana, New Jersey, New York, Oregon, Pennsylvania, Virginia, Washington, Washington D.C. and West Virginia (USDA-NRCS 1999, BONAP/MIP 1999). Rush skeletonweed is also present in Canada; being found in Ontario as well as in British Columbia (British Columbia 1999). 3. Sectors Affected and Magnitude of the Problem. Rush skeletonweed presently infests over 6.2 million acres of rangeland in the Pacific Northwest and California and is currently invading British Columbia and Montana. Infested land types include roadsides, railways, rangelands, pastures, grain fields, coastal sand dunes, and shaley hillsides in mountainous regions (Reed 1979; Sheley and Hudak 1995). In Australia , competition from rush skeletonweed reduced wheat yields by as much as 80%, resulting in estimated losses of more than $25 million (18.6 million due to lost of production and 1.4 million for direct control) (Cullen 1986). Although no similar economic studies on estimated losses in North America are known to us, we predict 1 a similar loss in infested grain fields and additional losses due to dramatically reduced rangeland forage production. 4. Consensus that the Weed is a Suitable Target for Control. Rush skeletonweed has not been placed on the Federal Noxious Weed List but has been listed as noxious by the following states/provinces: Arizona, California, Colorado, Idaho, Montana, Oregon, South Dakota, Washington, and British Columbia (New Invaders Database 1999, USDA-NRCS 1999). However, it should be noted that many state noxious weed lists are not very inclusive and tend not to include species which are not currently present in the state but which would pose a threat if introduced. Thus, rush skeletonweed is a larger threat than the current state weed lists reflect. Because of its importance as a weed, a biological control program was undertaken against rush skeletonweed in the 1970s that resulted in the successful introduction of three biological control agents. By the 1980s, these agents produced satisfactory control of rush skeletonweed in California and some areas of Washington. However, these agents do not provide effective control over most of the North American range of rush skeletonweed, particularly the cooler, interior lands of Oregon, Washington, Idaho, and Montana. As a result, a new program is underway to find, import, and establish a complex of new biological control agents capable of controlling rush skeletonweed in North America. Proposed Action We are requesting approval for the release of the of the root boring moth Bradyrrhoa gilveolella (Treitschke) to augment the biological control of rush skeletonweed in western North America. II. TARGET WEED INFORMATION Taxonomy of the Target Weed 1. Classification. Phyllum: Magnoliophyta Class: Magnoliopsida Order: Asterales Family: Asteraceae Subfamily: Cichorioideae Tribe: Lactuceae Subtribe: Crepidinae Genus: Chondrilla Species: juncea L. Common name: rush skeletonweed (approved common name - North American), also hogbite, gum succory, devil’s grass and naked weed.